ASoC: cs42l51: change cs42l51_of_match to static

cs42l51_of_match is only used in cs42l51-i2c.c now,
change it to static.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230725120917.513064-1-yangyingliang@huawei.com


Signed-off-by: Mark Brown <broonie@kernel.org>